Linda Goodman has an amazing talent for explaining astrology in a humorous way in which we can all relate and understand. I refer to this book a lot when I'm trying to "figure someone out". I personally have a library of Astrology books, but this is the one I most often refer to, followed in a close second by Linda Goodman's "Love Signs", and a puple book entitled "The only astrology book you'll ever need".
For anyone who is interested in astrology, even if they don't know a lot about it, this is a good book to start with!